2
https://raw.githubusercontent.com/njcodernoob/codility-java-solutions/master/DistinctSolution1.java
package com.challenges;

import java.util.HashSet;
import java.util.Set;

/*
 * 
 * Write a function

class Solution { public int solution(int[] A); }

that, given an array A consisting of N integers, returns the number of distinct values in array A.

For example, given array A consisting of six elements such that:

 A[0] = 2    A[1] = 1    A[2] = 1
 A[3] = 2    A[4] = 3    A[5] = 1
the function should return 3, because there are 3 distinct values appearing in array A, namely 1, 2 and 3.

Write an efficient algorithm for the following assumptions:

N is an integer within the range [0..100,000];
each element of array A is an integer within the range [−1,000,000..1,000,000].
 * 
 */

public class DistinctSolution1 {

	public int solution(int[] a) {
        // write your code in Java SE 8
        
        Set<Integer> nums = new HashSet<>();
        
        for (int i = 0; i < a.length; i++) {
            nums.add(a[i]);
        }
        
        return nums.size();
        
    }

}
